The company’s stock was trading at roughly $50 per share on Thursday afternoon, a low it hasn’t hit since its share price sunk to $48.63 in Sept. 2011. By afternoon, the stock was down roughly 17%.

Qualcomm (QCOM), based in San Diego, Calif., reported on Wednesday that its earnings fell to $1.1 billion from $1.9 billion a year ago. The chipmaker also forecast earnings per share of $0.80 to $0.90 for its current quarter ending in Dec., well below the $1.08 estimated by analysts in a Thomson Reuters poll.

The company says it is struggling to get Chinese customers to pay for licensing patents. It also recently underwent an activist investor-led corporate restructuring.

The nosedive has made Qualcomm one of the worst performing stocks in the S&P 500 on Thursday.